This program covers the long-standing development of laser microsurgical techniques that initially centered on ophthalmological applications and systems of interest in that field (pulsed carbon dioxide lasers and pulsed ND:YAG slit lamp-based laser systems). Its primary focus for the last 3 years has been in cardiological application of lasers, in particular laser angioplasty. In order to develop new laser microsurgical techniques in this new field, it was necessary to analyze a variety of laser sources and their tissue effects and the feasibility of transmission through flexible fiber optics. New sources such as Erbium:YAG (YLF) lasers coupled to zirconium fluoride optical fibers and excimer lasers coupled to fused silica fibers were examined, as well as more conventional sources (pulsed carbon dioxide and Nd:YAG lasers and continuous-wave argon and dye lasers). In collaboration with the Naval Research Lab, we have developed the new erbium laser microsurgery technology, beginning with feasibility studies and proceeding to development of a microsurgical prototype using zirconium fluoride fibers. Refinement of this system is primarily directed towards intravascular ablation (laser angioplasty), but includes applications to intraocular surgery (particularly to vitreal membranes, trabeculotomy, cataract surgery and corneal transplantation), destruction of renal stones, and endoscopic.